Purification of crude anthracene



, I No Drawing.

Patented Nov; 10, 1931 v UNITED STATES EPATENT OFFICE.

LLOYD c. DANIELS, or cRArro PENNSYLVANIA, ASSIGNOR, ,TO: THE sELnnNcon,- *2:

PANY, or PITTSBURGH, PENNSYLVANIA, nconroiwrroN or DELAWARE PURIFICATIONor" ca se ANrrin cn n This invention relates to crude anthracene. V

Crude anthracene contains as its main impurities carbazole andphenanthrene together with a certain amount of oily material ordinarilyreferred to as deadoils and minor amounts of other organic compounds. Inthe past crude anthracene has been purified by the use of varioussolvents which have low solvent power for anthracene, at least in thecold, but high solvent power for one or both of the main impurities.Examples of such solvents are pyridine, which dissolves both carbazoleand phenanthrene readily, and mononuclear aromatic hydrocarbons, such asbenzene, toluene and solvent naphtha, which dissolve phenanthrene.readily and have little solvent power for carbazole or anthracene inthe cold.

According to the present invention crude anthracene is treated with achlorinated aromatic hydrocarbon or a mixture of chlorinated aromatichydrocarbons. I have found that the chlorinated aromatic hydrocarbonshave a very high solvent power for phenanthrene and do not notablydissolve anthracene in the cold. WVhile the chlorinated aromatichydrocarbons in general show solvent power for phenanthrene, thechlorinated mononuclear hydrocarbons appear to show the greatesteconomy, and orthodichlorbenzene is the preferred solvent both becauseof its efliciency and its low price and ready availability. Thechlorinated aromatic hydrocarbons are all substantially immiscible withwater, a very important factor in the purification of crude anthracenesince it permits the recovery of the last traces of solvent by steamdistillation from both the refined product and the crude residues, aprocedure which is not feasible with solvents which dissolve in water toa considerable extent, such as, for example,

pyridine.

The invention will be described in greater detail in connection with thefollowingspecific examples which illustrate a few typical embodiments ofthe invention using some. of

the cheaper and more common chlorinated aromatic hydrocarbons assolvents.

purification of I Application filed. m 27, 1928. Serial o. 295,852;

lZ'ammpZe 1 400 kilos of -40% crude "anthracene are suspended in 2,000liters of orthodichlorbenzene in the cold and agitated for about twelverhours. The undissolved material is filter'ed off and containsapproximately ot antthracene and 23% of carbazole, the remainder beingmainly phenanthrene. The original crude anthracene contained only about30% of anthracene. Half of the solvent is removed from the mother liquorby distillation and the product separated out.- It contains about 62%anthracene and 217% carbazole.

The remaining solvent is distilled off and a residue is obtainedcontaining about 8.5% of anthracene and 6% of carbazole, the remainderbeing largely .phenanthrene with some dead oils.

' Similar results are obtained byusing monochlortoluene,monochlorben'zene or 12.3.dic hloror 2.5.dichlortoluene. v

Example 2 400 kilos of crudeianthracene containing -about 2230%anthracene are dissolved in 2,000 liters of orthodichlorbenzene at C. orhigher. More crude anthracene is added in portions of 25 kilos until itno longer dis solves. With the ordinary run of 30% crude anthracene thetotal amount'dissolved byvthe 2,000 liters'is usually about'700 kilos.200

liters of orthodichlorbenzene are added, the solution being maintainedat at least 80 'C.

'ature, or lower. The precipitate is filtered off and containsabout 52%of anthracene and its volume and allowed to cool. A product separatesout, containing about 45 anthracene and 24% carbazole.

The mother liquor is then completely I tllled off, using steam to removethe last. traces a of solvent and the product is a good grade of and isthen allowed to cool to room temperr:

crude j phenanthrene containi'nghvery little 'anthracene and carbazoleas impurities.

Ewample 3 Better results are normally obtainedwith iiio an excess ofsolvent and this appears to be generally true for all or the chlorinatedsolvents. 'lhus, for example, a 50% crude anthracene 1s recrystallizedfrom a minimum amount or orthodichlorbenzene which will ust dlssolve'theproduct at 250 0., the resulting anthracene contains about 02%anthracene and 56% carbazole, the first fraction containing about 61%anthracene and 24% caroazole. W hen a 50% excess of Ol'tllOCllrchlorbenzene is used the recrystallized product contains about 66%anthracene and ZaP/o carbazole and the first traction about 61%anthracene and 22.0% carbazole. filmllal' cene with a mixture oforthodichlorbenzole and pyridine.

9. The herein described method of refining crude anthracene, comprisingtreating the same with halogenated aromatic hydrocarbons of the benzeneseries in the liquid phase.

10. The herein described method of refining crude anthracene comprisingtreating the same with orthodichlorbenzole in the liquid phase. I

. Signed at Pittsburgh, Pennsylvania this 26th day of July, 1928.

-LLOYD C. DANIELS.

results are obtained with otherchlorinated aromatic hydrocarbons such asmonochlorbenzene or monobrombenzene.

The invention has been described in connection with the use ofchlorinated aromatic the step which comprises subjecting the crude Yranthracene to the action of a solvent containing at least onechlorinated mononuclear aromatic hydrocarbon.

2. In the purification of crude anthracene, V

the step which comprises subjecting the crude anthracene to the actionof a solvent containing orthodichlorbenzene. V v

3. In the purification of crude anthracene, the step which comprisesrecrystallizing the material from a solvent containing a chlorinatedmononuclear aromatic hydrocarbon.

4. In the purification of crude anthracene,

the step which comprises recrystallizing the material from a solventcontaining orthodichlorbenzene. r

5. The herein described method of refining crude anthracene comprisingtreating the same with halogenated aromatic hydrocarbon of the benzeneseries.

I 6. The herein described method of refining I anthracene comprisingtreating the anthracene with a mixture ofa halogenated aromatichydrocarbon of the benzene series and a liquid hydrocarbon.

7. The herein described method of refining anthracene comprisingtreating the anthracene with a mixture of a halogenated aromatichydrocarbon of the benzene series and pyridine. v

8. The herein described method of refining anthracene comprisingtreating the anthra-

